The OS X 10.7.4 update introduces a bug where you will receive the message “Problems were found with the partition map which might prevent booting” when attempting to use Disk Utility to verify/repair a volume that has been encrypted using FileVault 2. This appears to be a false-positive message, as the boot volume continues to work, but no one is for sure. Some people are decrypting their boot volume just to be safe. Once decrypted, the message is no longer reported when doing a verify/repair in Disk Utility.